The long term objective of this project is to improve our understanding of changes sperm undergo during capacitation by use of ESR spectroscopy and spin label techniques. An improved understanding of biophysical changes in sperm compartments and membrane integrity associated with capacitation should provide insight for new approaches to human contraception and in correcting problems of infertility. Water soluble spin probes and an appropriate broadening agent will be used to determine changes in volume and viscosity of aqueous compartments as well as changes in sperm membrane porosity. The viscosity and physical state of the inner and outer lipid membrane components will be probed using lipid spin labels. Spin labelled-protein-alkylating agents will be attached to intracellular and membrane proteins to determine the physical state of their local environments. To assess if capacitation involves increased membrane porosity of the acrosome, the water volume contained in the acrosome will be determined for guinea pig and rabbit sperm. Biophysical characteristics of membranes and aqueous compartments will be compared for sperm capacitated by two different in vitro methods with those characteristics of sperm capacitated in vivo. The role of albumin in rabbit sperm capacitation and the ability of decapacitation factor to reverse biophysical changes resulting from sperm capacitation will be determined. The percent of sperm having undergone the acrosome reaction will be determined in all experiments. Analysis of variance and Duncan's multiple range test will be used to detect differences (P less than or equal to .05) between non-capacitated and capacitated sperm and differences between methods of capacitation.